1. Field of the Invention
The present invention relates to an art concerning an electromagnetic actuator that generates an axial electromagnetic driving force between an inner axial member and an outer tubular member and relates to the electromagnetic actuator and an active vibration-control device and an active vibration-damping device using the same.
2. Description of the Related Art
Generally, for an active vibration-control device or an active vibration-damping device, which is referred as an active type, the electromagnetic actuator is used in order to obtain an oscillation force. The electromagnetic actuator, as disclosed in Japanese Unexamined Patent Publication No. JP-A-2011-109831 for example, has a structure wherein both axial sides of an inner axial member are elastically supported in relation to an outer housing member by plate springs and the inner axial member is assembled to be movable relative to the outer housing member in the axial direction. The electromagnetic force exerted between a stator and a mover acts on the inner axial member and the outer housing member, thereby providing an axial oscillation force.
In the electromagnetic actuator of the conventional structure as disclosed in JP-A-2011-109831 mentioned above, an outer housing metal fitting with a bottomed circular tube shape is used. The plate springs, coil members, and the like are assembled to the outer housing metal fitting as they are superposed from the side of the bottom of the outer housing metal fitting. In the assembly, it is impossible to visually check the bottom of the outer housing metal fitting, so that it is difficult to keep assembly accuracy of the plate springs and the coil members.
Moreover, if the plate springs and the coil members are superposed and assembled to the side of the bottom of the outer housing metal fitting, the electromagnetic actuator tends to suffer from interference of the plate springs in relation to the side of the inner axial member during the oscillation operation. Therefore, a means to resolve the problem is required, e.g., interposition of a separate spacer between the plate spring and the coil member, or use of a unique shape such as a stepped shape for coil-side yoke members as disclosed in JP-A-2011-109831. Thus, the conventional electromagnetic actuator is intricately structured and difficult to manufacture.